The committee’s Republicans appeared to have missed that memo. Instead, they toggled between sweet-talking Mr. Sessions — “This is so great to have you here today,” “I sure appreciate your service” — and demanding that he appoint a special prosecutor to investigate a raft of allegations, most half-baked if not entirely raw, against Hillary Clinton, her campaign for president and her husband, former President Bill Clinton.

From the supposedly crooked deal that Mrs. Clinton engineered to sell off America’s uranium to the Russians, to the Clinton-Democratic National Committee-F.B.I. conspiracy behind the dossier on Donald Trump, to the tarmac meeting in 2016 between Mr. Clinton and President Barack Obama’s attorney general, Loretta Lynch — no Republican talking point was left unspoken.

It’s not surprising that, after 10 months of the chaotic, scandal-strewn Trump presidency and a steady flow of revelations about the Trump campaign’s ties to Russia, Republicans in Congress are desperate to talk about something, anything, else. What better way to distract from the investigation of the current special counsel, Robert Mueller, than to call for a criminal investigation of the president’s defeated opponent?

Committee Republicans asked the Justice Department to appoint another special counsel back in July, and appeared frustrated that it hasn’t happened yet. “It sure looks like a major political party was working with the federal government” to gin up a dossier and get the F.B.I. to “spy on Americans associated with President Trump’s campaign,” Representative Jim Jordan of Ohio said. “Doesn’t that warrant naming a second special counsel?”

To his credit, Mr. Sessions did not take the bait. “‘Looks like’ is not enough basis to appoint a special counsel,” he said. But, in a letter on Monday, his department told the committee that it was weighing such a move.

Whether or not the department appoints a special counsel, the pressure to do so is clear, from both Republicans in Congress and Mr. Trump, who has threatened Mr. Sessions’s job if he fails to prosecute Mrs. Clinton. That’s what’s so alarming: the push for the Justice Department to undertake a politically motivated investigation of a president’s political opponent, and purely as revenge for an actual investigation already underway.

Meanwhile, Mr. Sessions spent most of Tuesday’s hearing as he has all the others he’s sat through this year — by not recalling things that one would think most people would. At his confirmation hearing in January, he testified that he’d had no contact with Russians during the 2016 presidential campaign. Turns out he met at least twice with the Russian ambassador, Sergey Kislyak. Last month, Mr. Sessions appeared before the Senate again and was asked if any Trump campaign surrogates had had communications with the Russians. “I did not, and I’m not aware of anyone else that did, and I don’t believe it happened,” he said. Wrong again: Mr. Sessions spoke with at least two members of the Trump campaign, Carter Page and George Papadopoulos, about their plans to travel to Russia, where, Mr. Papadopoulos said, he would meet with government officials.

The conversation with Mr. Papadopoulos was during a March 2016 meeting of the campaign’s foreign-policy committee, according to Mr. Papadopoulos’s guilty plea last month for lying to the F.B.I. about his Russia connections.

On Tuesday, Mr. Sessions said he “had no recollection of this meeting until I saw these news reports.” His explanation for his poor memory was that he couldn’t be expected to remember every detail from 2016, since the campaign “was a form of chaos every day, from Day 1.” No argument there.

An earlier version of this editorial incorrectly described the communications between Jeff Sessions and Carter Page during last year’s presidential campaign. Mr. Page told Mr. Sessions he was traveling to Russia, but not that he would be meeting with Russian government officials there.